412 
PROCEEDINGS OF THE ACADEMY OF 
Myalina imbricaria, n. sp.—Shell rather small, very oblique, inflated. 
Beak (of left valve) compressed, acute, incurved, scarcely rising above the 
hinge ; posterior margin straight, making a very obtuse angle with the hinge 
line ; ventral margin regularly curved ; anterior, with a rather deep sinus a 
little above the middle, and a slight projection in front of the umbo. Hinge 
line straight, equal to the greatest antero-posterior dimension of the shell. 
Umbo abruptly convex on both sides, but posteriorly blending with the flat¬ 
tened expansion below ‘the hinge. Surface strongly marked by imbricating 
lamellse. 
Length along the umbonal slope about 1*04 (100) ; this line forms with the 
hinge >Hne an angle of 29° ; length of hinge line *70 (67) ; angle formed with 
posterior border 53° ; projection of anterior margin beyond the beak '07 (67). 
Localhij}— Moscow, Hillsdale county, in the Marshall sandstone. 
This sji^pies differs from its analogue M. lamellosa , de Kon. (An. Foss. 126, 
pi. iii. 6) by its sharper posterior angulation, and deep anterior sinus in the 
margin * 
Myalina AViGULorbES.—Shell small, oblique, with subcentral beaks : scarcely 
rising above the straight hinge line. Right valve unknown ; left produced 
anteriorly just beneath the hinge ; anterior margins parallel, forming an angle 
of about 70° with the hinge line ; midumbonal slope forming the same angle, 
having its anterior declivity convex, its posterior at first convex, then slightly 
excavated, giving an extended appearance to the posterior margin, but with¬ 
out any perceptible isolation of a posterior wing ; ventral margin regularly 
curved. Surface marked by faint incremental lines. 
Length along umbonal slope *34 (100) ; length of hinge line *31 (91) ; 
greatest antero-posterior dimension *32 (94). 
Locality. —Marshall. 
Myalina pterine.®formis, n. sp.—Shell small, equivalve, obliquely elongate, 
with an alate posterior expansion, which is suddenly thickened above to form 
the basis of the straight elongated hinge line. Beaks subterminal, obtuse, 
incurved, elevated a little above the hinge ; midumbonal slope making an 
angle of about 35° with the dorsal margin; from the upper portion the de¬ 
clivity is steep to the hinge on the posterior side, while on the anterior side 
the shell swells out into a sort of pouch, projecting beyond the beak ; poste¬ 
rior margin of shell showing a sinuation just below the hinge, from which a 
regular curve sweeps around to the anterior side. Shell thin, with fine in¬ 
cremental lines. 
Length of shell along dorsal margin *44 (100); length from beak along 
midumbonal slope *38 (86); distance from beak to anterior extremity, 
*10 (22) ; to posterior *34 (78); diameter of shell through umbo *12 (24). 
Locality. —Pt. aux Barques, from a friable and ferruginous sandstone over- 
lying the grindstones. 
Pterinea, Goldfuss. 
Pterinea carpinata, n. sp.—Shell small, hinge line extremely elongate, 
posteriorly terminating in an angle of 40°, separated by a slight sinuation 
from the body of the shell; ventral margin transversely semi-elliptic ; ante¬ 
rior wing short, saccate ; anterior margin forming with dorsal line an angle 
of about 45°. Beak flattened, not elevated above the hinge ; umbonal slope 
terminating at the middle of the ventral border, opposite which is the greatest 
width of the shell; descent from the umbonal slope to the antero-ventral bor¬ 
der very abrupt. Surface of cast showing numerous faint concentric grooves 
which are most conspicuous in the postumbonal region. 
Length of hinge *65 (100) ; greatest width of shell *21 (32) ; convexity of 
right valve *06 (9); length of anterior wing '06 (9). 
Locality. —Grindstone quarry, Pt. aux Barques, with Rhynchonella cameri- 
fera, &c. 
[Sept. 
